Battery cables and On/Off switch

[Danidl]

If you just *have* to use a switch on the main power line, then you might as well just use a circuit breaker and get some real benefit out of it.

... Interesting suggestion not sure how relevant. Domestic circuit breakers are AC rated and would wear very badly on DC circuits. The vibration on a bike would juggle the mechanical parts and probably cause unintended trips. there would be mounting problems. As well as these things are larger and usually need There is a reason why cars still use fuses and there is an inline fuse on battery packs anyway

 

[danielrlee]

... Interesting suggestion not sure how relevant. Domestic circuit breakers are AC rated and would wear very badly on DC circuits. The vibration on a bike would juggle the mechanical parts and probably cause unintended trips. there would be mounting problems. As well as these things are larger and usually need There is a reason why cars still use fuses and there is an inline fuse on battery packs anyway

Who said anything about domestic circuit breakers? DC breakers are available in a wide range of amperages and voltages and as well as surge protection, provide a convenient way to disconnect your battery from the rest of the system.

Fuses are used in cars because they are cheap.

 

[Deleted member 4366]

Some people use a blade fuse as their on/off switch on their ebikes. I think the idea is more security when they leave the bike parked somewhere. Nevertheless, it makes a handy switch, and you get two functions for the price of one.
http://www.ebay.co.uk/itm/In-Line-standard-waterproof-Blade-Fuse-Holder-fuses-25a-25amp-kit-car-boat-bike-/280794485838?hash=item4160a7d44e:m:meMXSoRhDacPSV8gv_N-l8w

 

[danielrlee]

Some people use a blade fuse as their on/off switch on their ebikes. I think the idea is more security when they leave the bike parked somewhere. Nevertheless, it makes a handy switch, and you get two functions for the price of one.
http://www.ebay.co.uk/itm/In-Line-standard-waterproof-Blade-Fuse-Holder-fuses-25a-25amp-kit-car-boat-bike-/280794485838?hash=item4160a7d44e:m:meMXSoRhDacPSV8gv_N-l8w

Really? I can't believe you're recommending automotive blade fuses. Every single time I've used them on an ebike, they've ended up causing me nothing but trouble and I'm not the only one to experience this.

Do you bother with a fuse on your builds? If so, what do you use? I cannot believe you use these.

 

[Deleted member 4366]

I don't use fuses, but I know people that do. Maybe the ones that you used weren't high enough rating. What was your bad experience?

 

[Danidl]

Who said anything about domestic circuit breakers? DC breakers are available in a wide range of amperages and voltages and as well as surge protection, provide a convenient way to disconnect your battery from the rest of the system.

Fuses are used in cars because they are cheap.

I think this discussion is going down a path of a solution looking for a problem.
Properly rated fuses are extremely reliable very cheap, light weight and very long lasting. Electro mechanical circuit breakers, unless aircraft rated will be subject to false triggering due to vibration, and need to be periodically tested. They have only one redeeming feature .. resettable. Aircraft will use them because the ability to reset a circuit in a timely manner might be a matter of life and death.
If full isolation is not a requirement , there are plenty of electronic power control devices which can act in resettable current control mode.

 

[anotherkiwi]

My solution is to re-solder an XT60 on the wires when they get too pitted... It is scary the first time you see the spark but you get used to it. Question: which goes first, the male or the female XT60? Or both at the same time? After about 1500 km they are still providing a good connection between the battery and the controller.

 

[Danidl]

I don't use fuses, but I know people that do. Maybe the ones that you used weren't high enough rating. What was your bad experience?

.. no fuses ... not Even on the output line from the battery ?? Someone likes to live on the edge..... But since we are going to be "hit" by the viciousness of a solar eclipse in six months, maybe not worth trying.... Enjoy the lobster

 

[Danidl]

My solution is to re-solder an XT60 on the wires when they get too pitted... It is scary the first time you see the spark but you get used to it. Question: which goes first, the male or the female XT60? Or both at the same time? After about 1500 km they are still providing a good connection between the battery and the controller.

I think it is the cathode connection which experiences the erosion.

 

[Charliefox]

I did that on my first electric bike because it only gave full-power when I pedalled, which can be a bit inconvenient at times. It works as a sort of "standby" switch.

You have to be mindful that the controller uses about 4W of power all the time it's connected to the battery, so that's not like a switch on the ignition wire (when you have one), which more or less isolates the battery.

I have a third rabbit up my sleeve! I can reach backwards with my right hand and whip out the euro kettle type plug from the front of the carrier mounted battery.

 

[danielrlee]

You could be right and I've only used poor quality blade fuse holders, but I have tried three or four different types.

The problem was always the same – poor conductivity between the holder and fuse legs that eventually resulted in a melted fuse holder and wire insulation. Using a pair of pliers to cinch the connection helped a little, but only delayed the inevitable. Bear in mind that I was running around 25A when I gave up on them.

Nowadays I mainly operate in the 60-80A area, so DC MCB's are absolutely perfect for the task. I've only ever had one false trip in 1000's of miles (not sure why since was only drawing a few amps at the time), but they've always performed fantastically for me, successfully tripping the couple of times that they should have.

 

[awol]

I see those blade fuses are generally rated at 12v but my controller at max hits 42v @ 16a
If I fitted a car style 12v blade fuse do I still need a blade fuse near to 16a or will the fuse amps change with the voltage change?

 

[danielrlee]

I see those blade fuses are generally rated at 12v but my controller at max hits 42v @ 16a
If I fitted a car style 12v blade fuse do I still need a blade fuse near to 16a or will the fuse amps change with the voltage change?

A 16A fuse will still blow at 16A, even at 42V. The danger is that the higher the voltage, the greater the electrical arcing, although in practice, blade fuses contain enough fuse wire to extinguish a 42V arc.

 

[Deleted member 4366]

Voltage makes no difference. It's only the amps that count.

The reason they give a voltage rating is for the insulation and to stop people getting electrocuted when they try to replace the fuse when they use them on 400v.

 

[JohnnyBBadd]

The problem with brushless controllers is that they have one or more large capacitors across the battery connection inside the controller. The capacitor charges instantly when you connect, which means that you get an instant massive current that makes a large spark and a zap noise. The spark erodes any contacts. The higher the voltage, the bigger the spark. It can be quite intimidating trying to connect a 64v or 74v battery to a controller.

AFAIK, brushed motor controllers have their capacitors on the output side of the controller, so you don't get such a spark when you connect it.

I use these - they work and do not spark when connecting between the battery and motor.

 

[anotherkiwi]

I bet they may do but the black nylon hides the spark whereas it is visible in the yellow ones. There is a spark free XT90 on the market that has a resistor in it, I think the XT60 may be too small to put one in.

Mine only started sparking when I installed my lights which are always on (no switch). Before that they only sparked if the controller caps lost their charge.

 

[Deleted member 4366]

I use these - they work and do not spark when connecting between the battery and motor.

Every connector/switch will spark. It's just a question of how easily it gets damaged. The spark comes from the capacitor/s. The only way to stop it is with a pre-charge resistor.

 

[JohnnyBBadd]

I bet they may do but the black nylon hides the spark whereas it is visible in the yellow ones. There is a spark free XT90 on the market that has a resistor in it, I think the XT60 may be too small to put one in.

Mine only started sparking when I installed my lights which are always on (no switch). Before that they only sparked if the controller caps lost their charge.

Sorry, I meant to link to the anti spark XC 90's - my mistake!

 

[JohnnyBBadd]

Every connector/switch will spark. It's just a question of how easily it gets damaged. The spark comes from the capacitor/s. The only way to stop it is with a pre-charge resistor.

Sorry, I meant to link to the anti spark XC 90's - my mistake!